They can continue on their merry way - talking, chatting, being friendly. Being awkward, perhaps. The glowing walls don't seem to mind.

They are, however, leading steadily downwards towards something else. The walls continue to light their way, casting a deep violet glow on everything. They couldn't be blamed for not noticing the change at first. They might be able to dismiss the first one as living here, and doing no appreciable harm. But then there's another, and another. They scamper along the ground and along the walls, walking over and obscuring the glowing lines. Perhaps when they do that is when their form will become clear for the first time.

Spiders. Hundreds of them, running over the floor and your feet and onto the legs of your pants. One hopes you are not so very ticklish.